There has been known an internal combustion engine cooling system for a vehicle that cools an engine by circulating cooling water in an internal combustion engine (engine) to output a driving force for running a vehicle.
For example, in an internal combustion engine cooling system disclosed in JP-A 2010-163920, a head-side passage that circulates a cooling water for cooling a cylinder head and a block-side passage that circulates a cooling water for cooling a cylinder block are provided in an engine. At the time of warming up the engine, the quick warming-up of the whole of the engine is realized by preventing the cooling water from being circulated in the head-side passage to accelerate increasing the temperature of the cylinder head.
Moreover, in general, the cooling water circulating through this kind of internal combustion engine cooling system is used as a heat source of a heating heat exchanger (heater core) for heating a blowing air blown into a vehicle compartment that is a space to be air-conditioned in an air conditioner for a vehicle.
Thus, in an internal combustion engine cooling system for a vehicle disclosed in JP-A 2010-163897, when a request of heating a vehicle compartment is made while the engine is warmed up, the heating of the vehicle compartment is realized by guiding the cooling water flowing out of the head-side passage into the heater core and further by making the cooling water flowing out of the heater core bypass the block-side passage and flow into the head-side passage.
However, in the internal combustion engine cooling system disclosed in JP-A 2010-163920, when a heating request is made at the time of warming up the engine, the cooling water flowing out of the block-side passage needs to be made to flow into the heater core, which results in delaying the warming-up of the cylinder block side. Thus, this delays the warming-up of a portion (liner portion) of a cylinder in a cylinder block that slides on a piston to cause an impairment in fuel efficiency by a friction loss.
Further, in the internal combustion engine cooling system disclosed in JP-A 2010-163897, the cooling water flowing out of the head-side passage is supplied to the heater core, so that in order to secure a heat quantity to sufficiently heat the blowing air, the flow rate of the head-side cooling water circulating through the head-side passage needs to be increased. However, when the flow rate of the head-side cooling water circulating through the head-side passage is increased, the temperature of the cooling water flowing out of the head-side passage is made lower. Thus, the temperature of the blowing air cannot be sufficiently raised and hence quick heating cannot be realized.